iPhone Theft Prevention

Hello,

My wife and I have been iPhone patrons for the past four years. I do like the iPhone a lot and thanks to apple for its good products. That said, it's very painful when you lose your iPhone. My wife and I have had our iPhones stolen at some point and despite the find your iPhone app, we couldn't retrieve them because the thief turned the phone off. However this could have been prevented if turning the phone off required a password or something to prevent the stranger from turning off the phone. That way the find my iPhone app would be more useful in theft cases. Nobody really turns their phone off on a regular basis so I'm sure it won't affect iphone owners at all. Is it possible to have an update that requires a password to turn the iPhone?